In related art, a fixing device having a flexible tubular member, a nip member arranged inside the tubular member, a pressure roller forming a nip portion by sandwiching the tubular member between the nip member and the pressure roller, and a rigid stay supporting the nip member from the opposite side of the pressure roller is known (see JP 2011-137933). According to this technique, both end portions of the stay (both end portions in an axis direction of the tubular member) are biased toward the pressure roller by a biasing member, and thus the nip member is in pressure contact with the pressure roller via the tubular member.